Analysis Tools
mortality/aging
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• homozygotes are born at normal Mendelian frequencies and survive for at least >1 year
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growth/size/body
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• at 3-8 weeks of age, both female and male mice show a significant (~10%) reduction in body weight relative to wild-type controls
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behavior/neurological
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• homozygotes develop generalized seizures with tonic-clonic convulsions without loss of consciousness in novelty situations
• a typical sequence consists of three phases: partial seizures, tonic-clonic convulsions and very quite pausing
• seizure probabilities rise to 50% and 80% at 18 and 23 weeks of age, respectively
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nervous system
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• homozygotes develop generalized seizures with tonic-clonic convulsions without loss of consciousness in novelty situations
• a typical sequence consists of three phases: partial seizures, tonic-clonic convulsions and very quite pausing
• seizure probabilities rise to 50% and 80% at 18 and 23 weeks of age, respectively
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• although gross hippocampal architecture is normal, hippocampal volume is increased by 7%
• however, no differences in brain weight, brain volume, brain histology or cortical thickness and layering are observed
• F-/G-actin ratios in the hippocampus and in resting synaptosomes remain normal
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• after prolonged light exposure, retinal rod ribbon synapses exhibit an increased frequency of clathrin labelling at the plasma membrane
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• homozygotes show significantly increased SV diameters in hippocampal synapses and SV surfaces are less curved than wild-type; however, no differences in hippocampal synapse density, active zone length, SV density or number of docked SVs are observed
• after prolonged light exposure, retinal rod ribbon synapses exhibit significantly larger SV diameters
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• after prolonged light exposure, retinal rod ribbon synapses exhibit a 58% reduction in SV density
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• homozygotes display altered hippocampal network activity upon stimulation
• after induction with kainic acid, the power of gamma frequency oscillations is increased by >230% in hippocampal slices relative to wild-type slices
• upon application of bicuculline (a GABAA receptor antagonist), the frequency of epileptiform discharges is increased by >3-fold relative to wild-type controls while the amplitudes of discharges rise by >90%
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• FM1-43 dye recycling analysis in nerve terminals of cultured hippocampal neurons after moderate (300 APs at 10 Hz) and strong (800 APs at 80 Hz) stimulation revealed a trend towards reduced dye uptake after 300 stimuli (deltaF1) and significantly decreased dye uptake after 800 stimuli (deltaF2), suggesting defective activity-dependent SV endocytosis
• averaged deltaF2/deltaF1 ratio of individual nerve terminals is significantly reduced relative to wild-type neurons, suggesting impaired high-capacity retrieval of SVs
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• significant reduction in evoked EPSC (eEPSC) amplitudes upon an increasing strength of stimulation in CA1 pyramidal neurons
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• significant reduction in eIPSC amplitudes upon an increasing strength of stimulation in CA1 pyramidal neurons
• reduction is apparently larger for the inhibitory (eIPSCs) than for the excitatory system (eEPSCs)
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• whole-cell recordings from CA1 pyramidal neurons revealed significantly reduced frequencies of mEPSCs
• however, the peak amplitudes of mEPSCs are similar to those in wild-type neurons
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• whole-cell recordings from CA1 pyramidal neurons revealed significantly reduced frequencies of mIPSCs
• however, the peak amplitudes of mIPSCs are similar to those in wild-type neurons
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• short-term depression evoked by strong stimulations is significantly less pronounced in mutant hippocampal slices than in wild-type slices
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cellular
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• homozygotes show defects in presynaptic membrane trafficking processes, especially under high-capacity retrieval conditions, accumulation of endocytic intermediates, impaired activity-dependent SV retrieval, and defective synaptic activity
• recruitment of dynamins I, II and III to the curved membranes of liposomes is impaired; recruitment defects can be completely rescued by addition of recombinant syndapin I to mutant brain cytosol
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vision/eye
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• homozygotes show severe alterations in rod photoreceptor ribbon synapses after light exposure
• after acute light exposure, rod ribbon synapses display a 110% increase in endosome-like structures as well as accumulations of branched tubular structures
• after prolonged light exposure, rod ribbon synapses show massive membrane trafficking defects with numerous coated omega-shaped profiles at the presynaptic plasma membrane, in addition to branched tubular structures and a 170% increase in endosome-like structures
• after prolonged light exposure, SV sizes are shifted to larger SV diameters, and SV density is reduced by 58%
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reproductive system
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• fertility is reduced by ~30%
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